Various processes are already known for producing reinforcing preforms for axi-symmetrical pieces in composite material.
One of these processes consists in stalking rings of fibrous material and optionally bonding them together, for example by needling, in order to produce a preform which is thereafter densified to obtain the desired axi-symmetrical piece. This process is suitable for producing pieces of relatively small thickness, such as brake discs, but it is not particularly suitable when the pieces to be produced have a greater axial dimension.
Another known process consists in winding on a mandrel yarns, tapes or strips of fibrous material in superposed layers. The layers may be bonded together in different ways, such as by needling or sewing or by means of pins implanted on the surface of the mandrel, either so as to actually produce radial bonding of the elements, or to provide a passage for radial reinforcing elements which are inserted after the winding operation.